Analysis, optimization, and assessment of radioisotope thermophotovoltaic system design for an illustrative space mission

Abstract

A companion paper presented at this conference described the design of a Radioisotope Thermophotovoltaic (RTPV) Generator for an illustrative space mission (Pluto Fast Flyby). It presented a detailed design of an integrated system consisting of a radioisotope heat source, a thermophotovoltaic converter, and an optimized heat rejection system. The present paper describes the thermal, electrical, and structural analyses which led to that optimized design, and compares the computed RTPV performance to that of a Radioisotope Thermoelectric Generator (RTG) designed for the same mission. I RTPVs are of course much less mature than RTGs, but our results indicate thatwhen fully developed-they could result in a 60% reduction of the heat source's mass, cost, and fuel loading, a 50% reduction of generator mass, a tripling of the power system's specific power, and a quadrupling of its efficiency. The paper concludes by briefly summarizing the RTPVs current technology status and assessing its potential applicability for the PFF mission. For other power systems (e.g. RTGs), demonstrating their flight readiness for a long mission is a very timeconsuming process to determine the long-term effect of temperature-induced degradation mechanisms. But for the case of the described RTPV design, the paper lists a number of factors, primarily its cold (0 to 10°C) converter temperature, that may greatly reduce the need for long-term tests to demonstrate generator lifetime. In any event, our analytical results suggest that the RTPV generator, when developed by DOE and/or NASA, would be quite valuable not only for the Pluto mission but also for other future missions requiring small, long-lived, low-mass generators.

Modelado y fabricación de células fotovoltaicas de GaSb : Aplicación a sistemas termofotovoltaicos

“…Por ello, las mayores eficiencias atribuibles a los sistemas termofotovoltaicos resultaban muy prometedoras para sustituir los sistemas basados en termopilas por células fotovoltaicas de GaSb, manteniendo las fuentes de radiación basadas en radioisótopos y consiguiendo con ello sistemas de menor peso, requisito fundamental en todas las misiones espaciales. En [Schock94a] y [Schock94b] se analizó pormenorizadamente el diseño, construcción y rendimiento de un sistema termofotovoltaico basado en 256 células de GaSb y un generador térmico basado en pastillas de óxido de plutonio ( 238 PuO 2 ) y encapsuladas en iridio. Los cálculos y prototipos realizados mostraron la superioridad del sistema termofotovoltaico, con eficiencias que alcanzaban el 15,1% y densidades de potencia específica de 10,4 W/kg, frente al 7% y los 5,7 W/kg del sistema originario.…”